In the production of color photographic images, it is usually necessary to remove the silver image which is formed coincident with the dye image. This can be done by oxidizing the silver by means of a suitable oxidizing agent, commonly referred to as a bleaching agent, in the presence of halide ion, followed by dissolving the silver halide so formed in a silver halide solvent, commonly referred to as a fixing agent. Alternatively, the bleaching agent and fixing agent can be combined in a bleach-fixing solution and the silver removed in one step by use of such solution.
In the reversal processing of black-and-white photographic materials, a bleaching step is also utilized to remove photographically developed silver.
A wide variety of bleaching agents are known for use in photographic processing, for example, ferricyanide bleaching agents, persulfate bleaching agents, dichromate bleaching agents, permanganate bleaching agents, ferric chloride, and water-soluble quinones. A particularly important class of bleaching agents are the aminopolycarboxylic acid bleaching agents, such as an ammonium or alkali metal salt of a ferric complex of ethylenediaminetetraacetic acid. These complexes are used in both bleach compositions and bleach-fix compositions.
It has also been proposed heretofore to use peroxy compounds, such as hydrogen peroxide, as bleaching agents in both bleach compositions and bleach-fix compositions. Thus, for example, Koboshi et al, U.S. Pat. No. 4,277,556, issued July 7, 1981, describes a photographic bleach-fixing composition which is an acidic aqueous solution containing hydrogen peroxide and certain organic acids or alkali metal salts thereof; Idota et al, U.S. Pat. No. 4,301,236 issued Nov. 17, 1981, describes a photographic bleaching composition which is an aqueous solution containing hydrogen peroxide, an organometallic complex salt, and an aromatic sulfonic acid or salt thereof; and Idota et al, U.S. Pat. No. 4,328,306 issued May 4, 1982, describes a method of bleaching with hydrogen peroxide and an organometallic complex salt utilizing a replenisher composed of a first composition containing the hydrogen peroxide and a second composition containing the organometallic complex salt.
Bleaching and bleach-fixing compositions known heretofore suffer from serious disadvantages which significantly limit their usefulness in photographic processing. For example, ferricyanide bleaching agents are very effective but create substantial difficulties in regard to safe disposal. Persulfate bleaching agents and aminopolycarboxylic acid bleaching agents are preferred from an ecological point of view because they present fewer problems in regard to disposal of waste processing solutions in which they are present. However, the persulfate bleaching agents and aminopolycarboxylic acid bleaching agents suffer from the disadvantage that they provide a bleaching action which is undesirably slow for use in many photographic processes and frequently require the use of a bleach accelerating agent. It is toward the objective of overcoming this problem by the provision of a novel bleaching composition which is fast and effective and which is highly advantageous from an ecological standpoint that the present invention is directed.